Quiz 2.3

Describe the anatomy and physiology of "Myelin sheaths".

"Myelin sheaths" are made up on mostly fat, but also contain water and proteins. Myelin sheaths are responsible for surrounding the axon, which stabilizes electrical impulses by making sure the current goes where it's supposed to.

Compare and contrast "Schwann cells" and "oligodendrocytes".

"Schwann cells" wrap around the axon many times to form the myelin sheath and are individual cells. Schwann cells belong the the PNS, which extends to limbs. "Oligodendrocytes" have "arms" that wrap around multiple axons and can connect to various neurons. Oligodendrocytes belong to the CNS, which includes the brain and spinal cord. Both cells are types of glial cells, which protect neurons and provide structure.

Nerve

A bundle of thousands of axons.

Axons

A long or short tube that stabilizes electrical impulses as they travel through a neuron.

Myelin sheath

A tube that protects the axon and allows for faster electrical impulse transportation.

What are differences between axons and dendrites?

Axons carry messages away from your body and dendrites carry messages to your body. Axons are encased in myelin, and dendrites are not.

Describe the path of an electrical impulse as it moves through a neuron. You must use the words axon, axon terminal, dendrites, myelin sheath, nodes of Ranvier, synapse and neurotransmitters in your description.

Electrical impulses start in the dendrites on neurons. They are then sent through the cell body until the reach the axon. Once the impulse reaches the axon, it jumps from one node of Ranvier to the next instead of traveling through each myelin sheath, which can take some time. At the end of the chain of myelin sheaths (end of axon) the impulse goes through axon terminals until it reaches a synapse, where the electrical signal becomes a chemical called a neurotransmitter.

Schwann cells

Forms the myelin sheath and provides protection for the axon.

How do you think a person would be affected if myelin on his/her neurons was damaged or destroyed?

If the myelin in a person's nervous system was damaged they would most likely function more slowly since myelin aids in speeding up the rate at which impulses are passed throughout the nervous system.

Synapse

Impulses spread from axon of one neuron to dendrites of another.

What does an interneuron do?

Interneurons are responsible for making sure that signals are smoothly passed between motor and sensory neurons.

How is an interneuron structured?

Interneurons have short dendrites with short or long axons.

Dendrites

Long or short extensions of a neuron that connect to a cell body and start the transmission of the impulse through a nerve cell.

What does a motor neuron do?

Motor neurons are responsible for letting your body know when to coordinate a movement (outwards or inwards) (CNS). Relays messages from CNS to the rest of your body.

How is a motor neuron structured?

Motor neurons have short dendrites and a long axon

Describe one way in which neurons are similar to other cells in the body and one way in which they are different.

Neurons are similar to other cells in the body because they both have cell membranes and bodies that are filled with organelles, including a nucleus. Neurons are different from other cells because they have axons and dendrites to aid in sending impulses to the body.

What are "Nodes of Ranvier" and why are they important?

Nodes of Ranvier are the gaps between myelin sheaths are and important because they allow for impulses to pass more quickly through a neuron. Instead of traveling along the entire length of the axon by going through the myelin sheaths, impulses can "jump" from one node to the next until it reaches its next destination.

What does a sensory neuron do?

Sensory neurons are responsible for sending messages from receptors back to the CNS

What neurons are unipolar, bipolar, and/or multipolar?

Sensory neurons can be uni or bipolar. Motor neurons are multipolar. Interneurons are multipolar.

How is a sensory neuron structured?

Sensory neurons have long dendrites with short axon

In this activity, you read that there are billions of neurons in the human body that vary in size and somewhat in structure. Suggest and then support a reason why the body needs so many neurons.

The body needs so many neurons because all functions start in the brain. Neurons are cells which send chemical and electrical signals all throughout the body which lets your organs, muscles, etc know what to do.

How does the structure of each type of neuron relate to its function in the nervous system?

The structure of each type of neuron relates to its function by helping it process signals and knowing how to relay it to specific parts of your body. The structure of neurons helps communication between dendrites and axons.